: Accurate and early detection of small acoustic tumors is difficult with standard Auditory Brainstem Response (ABR) measures. As a result, expensive MRt is now used to screen patients suspected of having a tumor. However, most of those screened do not have tumors. Our long-term goal is the development of a compact cost-efficient screening device based on the Stacked ABR, a newly-developed ABR method for detecting small acoustic tumors. This device will insure imaging of patients with tumors while substantiafly reducing imaging of non-tumor patients. In Phase I, we (1) demonstrated that the Stacked ABR method detected small tumors with excellent sensitivity and good specificity in a large clinical population, and (2) developed basic hardware and software components for the commercial device. In Phase II, we will (1) optimize the Stacked ABR method to increase its clinical utility, (2) incorporate the method in a user-friendly prototype, and (3) validate the optimized method and evaluate the prototype in a multi-center Study. Thus, in Phase II, a commercially-viable prototype using optimized Stacked ABR algorithms will be developed, thoroughly tested, and independently validated. This work is crucial to our Phase III goal of developing a user-friendly cost-efficient commercially-available clinical system for the Stacked ABR. PROPOSED COMMERCIAL APPLICATION: Not Available